Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1996-06-11
1997-11-18
Krass, Frederick
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
528 89, 528 90, 528 93, 528 94, 528106, 528109, 2642096, 26421124, 26433112, 2643282, 525525, C08G 5968, C08B 6510
Patent
active
056888775
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of extending the low viscosity time for mixture of epoxy resin and hardener. More particularly, the invention relates to a method of extending the low viscosity time for resin of epoxy and hardener without significant lowering of the glass transition temperature (Tg), or the fraction of overall epoxy resin reacted.
German Patent 1,770,045 discloses aryl sulphonates as catalysts for the reaction of epoxide resins and polyamides. U.S. Pat. No. 4,728,676 teaches tertiary or quaternary ammonium salts of alkylating or acidic esters of organic phosphoric acids or phosphonic acids as catalysts of the reaction between epoxides and polyisocyanate. U.S. Pat. No. 4,728,676, Column 2, lines 13-15.
Of course, there is the general background of the art of epoxide preparation, polymerization, and utility widely disclosed in texts such as Lee and Neville, Handbook of Epoxy Resins, McGraw-Hill Book Company, 1967; Kirk Othmer, Encyclopedia of Chemical Technology, "Epoxy Resins", Volume 9, (1980).
It is an object of the present invention to provide a reactive resin mixture having an extended pot life for amine cured epoxy resin articles. Extended pot life generally corresponds to a delayed gel point. It is a further object of this invention to provide a method of increasing the "wet-out" of reinforcing fibres of epoxy resin composite articles. Further, it is an object of this invention to provide an improved method of molding an epoxy resin reinforced article by the process known as Resin Transfer Molding (RTM) by reducing the in-mold time of each part. The improved RTM process is characterized in part by a longer period of low viscosity for resin injected into the RTM mold, rapid cross-linking, and improved strength upon demolding of the demolding article as compared with prior art RTM processes, and articles prepared by RTM processes. This improved RTM process makes possible significant production economies.
Further objects of the invention include a reduction of distortion of RTM articles because of reduced shrinkage related to lowered curing temperatures.
A further object of the invention is to provide a process for coating substrates with epoxy films such as wood and plastics which are sensitive to elevated temperatures. Further, an energy saving occurs when powdered epoxy coatings are cured at 110.degree. C. to 120.degree. C. rather than the 150.degree. C. to 200.degree. C. required to cure epoxy coatings of the prior art.
Further, the invention has an objective to provide a hand lay-up-vacuum/pressure bag molding method of making a reinforced epoxy resin article. This invention provides hand lay-up method improved by having a longer time interval in which the epoxy resin is preserved at a lower viscosity to facilitate handling, yet without compromise to the length of the overall molding cycle. This is to say the interval of low viscosity of the mixture of resin and hardener is extended by the method of the invention, but because the cure time is maintained, or is shortened, the overall cycle time is nearly the same as, or shorter than, the cycle ti me of the corresponding prior art.
For casting and potting of epoxy resin, the invention has as an object, the extension of the interval of low viscosity of epoxy resin to facilitate the escape of gas trapped within the mold, and thereby to provide void-free castings without an increase of, or including a decrease of, mold cycle time. These and other objectives, and advantages will become apparent from the following further explanation description, examples and claims.
Usual active catalysts known in the art for epoxy-amine curing compositions are acids which when contacting the amine curing agent form immediately the corresponding ammonium salt which is believed to be the active catalytic species. The present invention describes a method of preparing the ammonium salts at a kinetically controlled reaction rate by using as catalyst precursor, an alkylating ester of the corresponding acid. Immediately after contacting the acid ester with th
REFERENCES:
patent: 3666721 (1972-05-01), Godfrey
patent: 4988549 (1991-01-01), Meyer et al.
Chemical Abstracts 113:25242, "Polyamide-Based Multilayer Moldings Containing Thermosetting Resin Layer", Meyer et al.
Derwent Abstracts 72-16726T/11, "Accelerator for Polyadduct Formation Between Epoxy Compounds and Nitrogenous Compounds".
Derwent Abstract 92-295676.
Gan Joseph
Hayman Richard J.
Koenig Raymond A.
Krass Frederick
The Dow Chemical Company
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